Optical encoder



G. A. HARRIS OPTICAL ENCODER Sept. 2, 1969 2 Sheets-Sheet 1 Filed Sept. 5. 1967 11ml: calmn- Q 0 r V m T V W m /T .1 w w; 2 2 79 2 (5. A. HARRIS OPTICAL ENCODBR Sept. 2, 1969 2 Sheets-Sheet 2 Filed Sept. 5, 1967 fl0 U 1 2% 7. J WU n0 1 0m a CC 1 1 1 .1 C c ornfnnn UUDD. P P n UMUD H T w w WK United States Patent 3,465,099 QPTHCAL ENCUDER George A. Harris, San Ramon, Calif., assignor to Friden, inc a corporation of Delaware Filed Sept. 5, 1967, Ser. No. 665,588 lnt. Cl. 1104115/18, 15/12, 15/16 11.5. (Ii. 178-47 Claims ABSTRACT OF THE DISCLOSURE A photoelectric keyboard has key-operated shutters controlling two or more groups of light channels, the groups being assigned to alternative characters, or alternative codes. One or more shift keys operate shift control shutters that normally obscure all but one group, but when depressed obscure that one group and activate others.

The present invention relates to photoelectric encoders, and more particularly to photoelectric keyboards for teletypewriters, computer inputs, and the like.

Certain prior coding systems provide the same singlebit difference between the codes for the two alternative characters of each key. Thus in the system of US. Patent No. 2,408,754 to Bush, a shift key simply obscures a single light channel to change any otherwise-lower-case character to a capital. This requirement for a common relationship between the alternative codings limits the versatility of the system. A prior system employing an eightbit photoelectric encoder has provided fully-independent, alternative characters and alternative codes by gating the electric output, but a 60-key keyboard and eight-bit code typically requires 1000 diodes for each alternative. US. Patent No. 2,438,825 to Roth discloses a photoelectric encoder providing alternative characters wherein the groups of code-element channels have separate lamps, separately energized. The device of the present invention is simpler and less expensive.

In accordance with my present invention, one or more shift keys of the keyboard, when actuated, move lightobscuring shields into one group of light channels and out of another for making said one group inactive and the other group operative.

These and other objects of the invention will be apparent from the following description of one specific embodiment thereof, taken in connection with the drawings,

\ wherein:

FIG. 1 is a fragmentary, partially sectional, plan view of a keyboard embodying my present invention;

FIG. 2 is a right elevational section of my keyboard taken substantially as indicated by the lines 22 in FIG. 1;

' FIG. 3 is a fragmentary, exploded, isometric view for schematically showing the relations of the lamp, mirror, mask, shutters and photocells of the device of FIGS. 1 and 2;

FIG. 4 is a table summarizing the action of the shift control shutters in the device of FIGS. 1-3;

FIGS. 5 and 6 are schematic views for illustrating the action of the shutters;

FIGS. 7 and 9 are partial views similar to FIG. 3 showing modifications; and

FIGS. 8 and 10 are tables, similar to FIG. 4, summarizing the actions of the modifications of FIGS. 7 and 9.

A photoelectric keyboard, or encoding device, shown in FIGS. 1 and 2, has many, such as sixty, similar shutters 10. Each such shutter has twenty-four rectangular recesses, or apertures, 12 arranged in two rows as seen in FIG. 2.

Patented Sept. 2, 1969 Some of these apertures are only partially open, being partially closed by light-obscuring shields 14. Preferably the shutters 10 are molded of a light weight plastic with the apertures 12 completely closed by the thin shields 14. The individual shields may then be punched out as required for the coding. Each shutter 10 moves vertically between stops 18 and 20 (FIG. 2) a distance slightly greater than half the height of its apertures 12. In this motion, the shutter is guided by lower stems 22 and 23 and upper key stem 24 which fit holes in the case of the structure. The upper stem 24 carries a key top 26 and an elastic 'boot 28 which biases the shutter up against its stops 18. The several shutters have their stems 22, 23 and 24 in various positions as shown in FIG. 2., to accommodate the four-row arrangement of the key tops.

The shutters 10 lie closely adjacent so that their aligned apertures 12 form light channels through the whole assembly of shutters. A lamp 32 (FIGS. 1 and 3), and a mirror 34, which constitutes a section of a paraboloid, direct light into all twenty-four of the channels, and, when those channels are open, onto twenty-four photoelectric cells 36. The recesses 12, which show in FIG. 2, appear only on one side of each shutter. Consequently, in FIG. 3 the openings show only where the shields 14 have been cut out.

Stationary shutters, or masks, 29 and 30 located at the two ends of the array of shutters 10, as seen in FIGS. 1 and 3, each has twenty-four openings 31. These openings are aligned with the normal positions of the lower halves of apertures 12, that is the positions occupied by those lower halves when the shutters 10 are in their upper, normal positions. With respect to each of the twenty-four light channels, the corresponding openings 31 in these masks 29 and 30 define the limits of the effective beam of light. The close spacing of the shutters 10 helps to prevent light in one channel from reaching the photocell of another.

Thus the twenty-four light channels through the array of shutters 10 coincide with the bottom halves of apertures 12 when the shutters are in their upper, normal, positions, and with the top halves of those apertures when the keyboard keys are depressed for lowering those shutters.

The twenty-four light channels and the respective apertures 12 of the shutters 10 are arbitrarily assigned in three groups of eight as indicated by the brackets 38 and 40 in the schematic perspective of FIG. 3. Each of these groups is used alone under control of the shift keys and shift control shutters, as will be explained.

Each photocell 36 in each of the three groups is connected in parallel with one of the photocells in each of the other two groups so that the keyboard has only eight photocell outputs. For example, the eight light channels of each group and corresponding shutter apertures and photocells, as seen in FIG. 3, maybe numbered, beginning in the upper left-hand corner of the group from 1 to 8. Then the three No. 1 cells may be connected in parallel, the three No. 2 in parallel, etc., as indicated by connections 37.

Most of the shutters serve as character encoders for indicating letters of the alphabet, numerals, punctuation, special characters, and control instructions, as required by the apparatus with which the keyboard is used. Such shutters have the bottom halves of all their apertures 12 open, as shown for shutters 52 and 54 in the schematic perspective of FIG. 3, so that, when those shutters are in their normal, upper, positions, they do not obscure the light or block it from the photocells 36. In each such character shutter, such as 52 and 54 in FIG. 3, the upper half of one or more apertures 12 is closed by lightobscuring shields 14 according to the codes assigned to the characters or functions of that particular shutter.

3 When the shutter is depressed, such shields block the light from the corresponding photocells 36.

In each character shutter, such as 52 and 54, one light channel of each group serves as the strobe. As the key and shutter are depressed, the strobe channel is the last of the group to obscure its photocell 36 for actuating its electric circuit. In a known manner, the strobe photocell thereby enables an AND gate for transmitting the code bits from the other photocells to the system, and, since it acts after the others, it insures that those other photocells read the code correctly. As seen in FIG. 3, the strobe apertures of shutters 52 and 54 are the second, sixth and tenth from the left in the upper row of each shutter. These apertures have shorter light-obscuring shields than the other apertures.

Two of the shutters 10 are shift-control shutters, shown at 42 and 44 in the schematic perspective of FIG. 3. The purpose of these is to leave only one group of eight apertures unobscured at one time. Like the character shutters, the shift control shutters have larger openings in the strobe channels.

For convenience and clarity, both in the description and in the claims, the three groups of apertures 12 and the corresponding three groups of light channels and photocells 36 are arbitrarily designated first, second and third as indicated at 38 and 40 in FIG. 3. Thus, in FIG. 3, in each shutter, the eight left-most apertures (4 in the upper row and 4 in the lower row) constitute the first group, the center eight. apertures (4 in each row) make the second group, and the right-most eight apertures (4 in each row) are the third group. Further, the two shift control shutters 42 and 44, operated by shift keys of the keyboard, are designated first and second as also indicated in FIG. 3. In the claims, the recitations of first, second and third groups, and first and second shift-control shutters, can be read directly on the first, second and third groups and shutters 42 and 44 as described in the specification.

The foregoing actions of the shutters are illustrated schematically in FIGS. 5 and 6. FIG. 5 shows only the two apertures at the leftmost end of each shutter in FIG. 3. These apertures are in the first group. However, it shows the opposite side from that seen in FIG. 3, and the full recesses 12, as seen in FIG. 2, shown here. Shutter 52 is shown in solid lines in its upper position 52A. Shutters 54 and 42 are shown in solid lines in their upper positions. Shutter 44 is shown in solid lines in its upper position 44A. With all of these four shutters in their uppermost positions, light passes through open channels to the corresponding photocells 36. Under this condition if the character shutter 52 is depressed to its lower position 52B, shown in dotted lines, the lower of the two light channels shown here is obscured for darkening the lower of the two photocells 36. Alternatively, if the shift control shutter 44 is depressed to its lower position 44B, shown in dotted lines, it obscures both of the light channels, these being light channels of Group 1, and makes these lights channels of Group 1 inactive.

Similarly, FIG. 6 shows the two apertures at the other ends of the same shutters, i.e., the rightmost ends in FIG. 3, the two light channels shown here being part of Group 3. Here in FIG. 6, the character shutter 52 is shown in solid lines in its upper, normal, position 52A. Shutters 54 and 42 are shown in solid lines in their upper positions. Shift control shutter 44 is shown in solid lines in its lower position 44B which is the position required for operation of this Group 3. In the solid line positions of these shutters, these Group 3 light channels are open so that the system responds to shields 14 in the apertures in Group 3 of the character shutters 52 and 54. For example, character shutter 52 is shown in dotted lines in its lower position 52B where it obscures the upper of the two light channels shown in this figure. When the shift control shutter 44 is in its upper position 42A, shown here in dotted lines, it obscures the light beams of this Group 3 and leaves this Group 3 inactive.

Both of the shift control shutters 42 and 44 have the lower halves of their apertures 12 in the first group (the leftmost eight apertures of each shutter as seen in FIG. 3) open, so that when both of these shift control shutters are in their upper, normal, positions they leave the light channels of this first group open to permit the illumination of the photocells 36 of this Group 1 to be controlled by the depression of the character keys. The first shutter 42 has its second group (center eight apertures) closed in the bottom half to normally obscure all the channels of this second group, and similarly, the second shift control shutter 44 has the apertures of its third group (rightmost eight apertures in FIG. 3) closed to normally obstruct the light in this Group 3. Consequently, with both of the two shift control shutters 42 and 44 in their upper, normal, positions, the light channels of Group 1 are open and Groups 2 and 3 are blocked and inactive, so that the depression of the character keys (one at a time) encodes the output according to the coding in the Group 1 apertures of the character keys.

The first shift control shutter 42 has the upper halves of its apertures 12 open in Group 2 (the center eight apertures), so that when this first shift control key 42 is depressed it obscures Group 1 and opens Group 2. The second shift control shutter 44 has openings in the lower halves of its apertures in Group 2 (the center eight apertures) open. Accordingly, the depression of only the first shift key 42 leaves only the Group 2 light channels active so that the system responds to the coding in the Group 2 (center eight) apertures of the character shutters such as 52 and 54.

The second shift control shutter 44 has the top halves of its apertures open in Group 3 (rightmost eight apertures in FIG. 3) so that when this second shift control shutter is depressed it not only closes Group 1 but opens Group 3. The first shift control shutter 42 has the lower halves of its Group 3 (rightmost eight apertures in FIG. 3) open. Consequently, with only the second shift control shutter 44 depressed, the light channels of Groups 1 and 2 are blocked and only this Group 3 is active. In this condition the system responds to the coding in the Group 3 apertures (rightmost apertures in FIG. 3) of the character shutter such as 52 and 54.

It is to be noted, in FIG. 3, that when both of the shift keys 42 and 44 are depressed, all of the light channels are blocked. In this condition the Group 1 channel is blocked by both of the shift control shutters 42 and 44, Group 2 is blocked by shutter 44 and Group 3 is blocked by shutter 42.

The table of FIG. 4 summarizes the operation of the shift control shutters 42 and 44 of FIG. 3. The numbers in the top row 56 of this table indicate that their respective columns relate to the first, second and third groups of light channels. The second row 57 indicates that in each column, the left side relates to the first shift control shutter 42 and the right side to the second shift control shutter 44. The first column 64 indicates whether the respective shift control shutters are up or down and the other columns show which groups of channels are closed by each shutter. Th-us, row 58 shows that when both shift control shutters are up, Group 2 is closed by the first shutter and Group 3 by the second shutter. Similarly, row 59 indicates that when the first shift control shutter is down and the second up, Group 1 is closed by the first shutter and Group 3 by both shutters. Row 60 shows that with the first shift shutter 42 up and the second shift shutter 44 down, the first group is closed by the second shutter, and the second group by both shutters. Finally, row 61 shows that with both shift control shutters down Group 1 is closed by both shutters, Group 2 by the second shutter and Group 3 by the first shutter.

It may be objectionable to permit the system to be made inoperative by the simultaneous depression of both of the shift keys. It can be made operative under this condition by modification of one or the two shutters 42 and 44. The table of FIG. 4 shows that in each of two different conditions, the shutter that closes a group in row 61 also is an extra shutter in another row. These are the light obscuring shields operable in the down condition in Group 2 of shutter 2 and Group 3 of shutter 1. One of these could be removed.

For example, the second shutter 44 may be modified by omitting all light obstructions in the second group, as shown for shutter 45 in FIG. 7. The operation of the two shutters 42 and 45 is summarized in the table of FIG. 8. As shown there, with both shutters up, Group 1 is open, Group 2 is closed by the first shutter and Group 3 is closed by the second shutter. With the first shutter down and the second up, Group 1 is closed by shutter 1, Group 2 is open, and Group 3 is closed by both shutters. With the first shutter 42 up and second shutter 45 down, Group 1 is closed by the first shutter, Group 2 by the second shutter, and Group 3 is open. With both shutters down, Group 1 is closed by both shutters, Group 2 is open and Group 3 is closed by the first shutter. Thus, with the first shutter 42 down, the same results are obtained whether the second shutter is either up or down. This arrangement has the advantage that the system operates in all four of the possible combinations of positions of the two shift control shutters 42 and 45. The arrangement has the further advantage that one of the two shift-control keys (the one for shutter 42) has priority over the other. Such priority is desirable, particularly for the control functions.

In spite of the inability of the system to produce improper codes with the shift control shutter arrangements of FIGS. 3 and 7, it still may be desirable to mechanically interlock the two shift control keys to prevent their simultaneous depression. If such an interlock (not shown) is provided, the shutter arrangement of FIG. 9' can be used. There the second shift control shutter 45 is the same as shutter 45 in FIG. 7, which is the same as shutter 44 in FIG. 3, except that no light obscuring shields are provided for the light channels of the second group. Also, in FIG. 9, the first shift control shutter 43 is like the shift control shutter 42 of FIGS. 3 and 7, except that no light obscuring shields are provided for the Group 3 light channels. The operation of the shutters 43 and 45 in FIG. 9 is summarized in the table of FIG. 10. Thus with both shift control shutters up, Group 1 channels are open, Group 2 is blocked by the first shutter 43 and Group 3 is blocked by the second shutter 45. With the first shift control shutter 43 down and the second shutter 45 up, Group 1 is blocked by the first shutter, Group 2 is open, and Group 3 is blocked by the second shutter. With the first shutter 43 up and the second shutter 45 down, Group 1 is blocked by the second shutter, Group 2 is blocked by the first shutter, and Group 3 is open. If the two shift keys could be depressed simultaneously, both Groups 2 and 3 would be open and the coding would be confused. The interlock is relied on to prevent this condition.

The shift control shutters, such as shutters 42 and 44 of FIG. 3, permit each character key to alternatively enter two or more different characters, or instructions, as does the shift control on the usual typewriter. Thus with both shift keys up, in the normal position, Group 1 is open and, for example, may permit the entry of capital letters, numerals, certain punctuation and certain special characters. With only the second shift key (shutter 44) depressed, Group 3 is open and this condition may permit the entry of lower-case alphabetical characters with the same or different numerals, punctuation and special characters. With only the first shift key 42 depressed, the same character keys may be used for entering operating instructions. If the keyboard is controlling a typewriter-like printer, these instructions may include l ne spacing, carriage return, paragraph indentation, page advance, and the like. If the keyboard is connected to a computer, these instructions may call for arithmetic 6 operations, the entry or retrieval of information, and the like.

Alternatively, the three groups of light channels may be employed for transmitting information in alternate codes. For example, Group 1, the normal operation, may encode the information in the Baudot code, Group 2 in the ASCII code (American Standard Code for Information Interchange), and Group 3 may provide for the entry of numbers in binary-coded decimal form.

When the shift keys are used for alternative characters, that is when each character key indicates two or more characters according to the position of the shift keys, it may be that in one shift condition not all of the keys are required. In such a situation, the shutter may be coded to indicate the same character as in another shift position, the apertures in that group, particularly the strobe aperture, may be provided with no shields at all so that the key does nothing in that group, or all apertures in that group may have shields in the upper half so that depression of that key obscures all photocells in that group, as may be preferred for the particular use to which the keyboard is put.

It would be possible to operate the system with only one strobe channel to serve all code groups. However, it is preferable to employ a separate strobe for each group, and to control it with the shift shutters just as the other channels are. This arrangement is especially advantageous when certain character keys are inactive in certain groups. If activation of the strobe control in such situations is avoided, then the electronic system need not have logic for recognizing and rejecting a strobe-only condition.

While the specific embodiments here shown and described employ one or two shift keys, and two or three alternative 7-bit codings, it will be apparent that the invention is applicable to systems with more shift functions, more alternative codings, and more or fewer bits per character.

The optical, self-contained keyboard of the present invention provides completely independent codings for the several alternative characters and encoding patterns assigned to the keys, and provides it simply and economically.

What is claimed is:

1. In a photoelectric coding device comprising:

(a) means providing a first and a second group of light channels, each said channel corresponding to one element of a code;

(b) output means including light responsive elements arranged to be irradiated by light passing through said channels;

(c) movable, encoding, input shutters each having at least one light-intercepting shield in a channel of each of said groups;

(d) each said input shutter having an inactive position in which it obscures none of said channels, and being movable to an active position in which the shields thereof reduce the light transmitting ability of their respective channels;

the improvement including:

(e) a movable shift-control shutter having shields for all said channels and being movable between one position in which the shields thereof reduce the light transmitting ability of all the channels of said second group but not of said first group, and a second position in which the shields thereof reduce the light transmitting ability of all of the channels of said first group but not of said second group; and

(f) means providing a third group of light channels and a second shift control shutter;

(g) said second shift control shutter having a first position in which it obscures the channels of said third group and not of said first group, and a second position in which it obscures the channels of said first group and not of said third group.

2. The combination of claim 1 wherein said first shift control shutter obscures the channels of said third group when in its second position, but not when in its first position.

3. The combination of claim 1 wherein (h) said first shift control shutter obscures the channels of said third group when in its second position, but not when in its first position; and

(i) said second shift control shutter obscures the channels of said second group when in its second position, but not when in its first position.

4. The combination of claim 3 wherein said coding device includes a manual keyboard and said shutters are operable by the depressable fingertip keys thereof.

5. The combination of claim 1 wherein each of said groups of light channels includes a strobe channel, the

light responsive element of which controls the outputs of the light responsive elements of the other channels of that group.

References Cited UNITED STATES PATENTS 2,408,754 10/19'46 Bush 178--81 2,641,753 6/1953- Oliwa 17817 3,104,388 9/ 1963 Balenger 17817 3,369,643 2/ 1968 Avgerinos et a1. 197-14 XR THOMAS A. ROBINSON, Primary Examiner US. 01. X.R. 

